This invention relates to a transmitter for a surveillance camera, and a surveillance system, and more particularly to a transmitter for transmitting images taken by a surveillance camera to a television receiver.
Among prevailing transmitters for transmitting images taken by a surveillance camera to a television receiver are, typically, those which come with door camera systems and video door phone systems. Each of these systems employs a surveillance camera provided at a front door or the like for security purposes, and commonly includes a wired means of communication through which images taken by the surveillance camera are transmitted to the receiver and displayed on a monitor thereof. Accordingly, necessary wiring of a power cord and a video signal transmission line produces a burdensome wiring task, and rather finding room for the wiring is necessitated.
On the other hand, radio transmission techniques are disclosed, for example, in Japanese Laid-Open Patent Application, Publication No. 2002-77893, in which power is supplied from a solar battery as well as storage batteries, and images taken by a camera are transmitted through a wireless means of communication to a receiver and displayed on a monitor. The combination of the solar battery and the wireless signal transmission method as above would appear to eliminate the disadvantages derived from the wiring.
However, the aforementioned radio transmission techniques with a solar and storage battery power supply would produce practically nonnegligible expenses. Moreover, the use of the solar battery requires installation thereof in a location of sufficient solar irradiation, and the storage battery intrinsically has the problem of a limited life.
Meanwhile, in order to receive television broadcasting, the ordinary households are equipped with an antenna for receiving radio signals broadcast over airwaves; the radio signals are amplified by a booster installed outdoors, led into the house and distributed to a television receiver. Between the booster and the television receiver is provided a booster power supply that supplies the booster with a direct current through an extra channel superposed in a coaxial cable that is normally used as a lead-in for the antenna.
The present invention has been made with consideration given to the above circumstances, and it is an object of the present invention to provide a transmitter for a surveillance camera, and a surveillance system, which utilizes an antenna lead-in wire that has already been wired in ordinary households, and thereby obviates the need for employing a solar battery or storage batteries for power supply, and makes wiring task for installation simplified.